This invention relates to reducing air drag on the rear surface of box shaped transport vehicles.
The ideal shape for the least aerodynamic drag would be the teardrop-rounded in front and pointed in the rear. However transport vehicles have been designed for cargo volume and structural strength. With the possible exception of the streamlined train, that recognized aerodynamic drag with their relative early speeds, transporting vehicles accepted the basic box shapes as cargo effective. Engines of sufficient power with multi speed transmissions overcame the aerodynamic drag and not until the increase in fuel costs did the effort to reduce drag begin in earnest. Since that time many deflector type devices have been used to provide the smoothed flow of air over the front of the vehicle. These proved to reduce drag and therefore saved fuel. Some attempts have been made to reduce drag, caused by the low pressure separated wake behind the vehicle, which is an important contributor to aerodynamic drag. Some of these attempts have proven too expensive or too complicated due to access requirements to the cargo via the rear doors of the vehicle.